Distribution Of Diatoms Research Articles

On the type specimens of Fragilaria siamensis Østrup, its transfer to Fragilariforma and comments on the biogeography of the genus

Biogeography is a valid scientific endeavour for exploring diatom distributions because the concept of endemism is generally accepted and not considered an irrelevant idea – endemism is taken seriously because it has been documented for many species in many areas around the globe. But to study biogeography meaningfully one does not just need the recognition of endemism. What is required is a problem, such as explaining the diversity of species or species groups in the Southern hemisphere. This requires the identification of species or species groups that are demonstrated to be endemic in at least some of the areas of interest and are related in a very specific way (monophyly). This paper deals with the genus Fragilariforma, which has ca. 30 + included species (taxa) that can be divided into a Northern component and a Southern component, the latter potentially speaking to the origin of the southern hemisphere biota.

Characterization of biotic and abiotic signatures of modern lake sediments of western India, and its palaeo-environmental implications

A multi-proxy study of biotic and abiotic components was conducted on surface sediment samples from six lakes/wetlands located along the western transitional boundary of the contemporary Indian Summer Monsoon (ISM) in the Indian Subcontinent. The primary goal is to assess the suitability of various proxies as representatives of modern vegetation, environmental and climatic conditions. The collected data indicate significant variations in the composition and density of pollen in response to climate-induced and anthropogenic ecological changes throughout the northwest India transect. The palynological studies from eastern Rajasthan shows high forest elements in comparison to western Haryana and western Uttar Pradesh. In addition, the palynological data was juxtaposed with other biotic proxies such as diatom and isotopic studies, along with geochemical proxies and paleomagnetic data of the surface lake sediments. The presence of marker pollen taxa including Cerealia type Poaceae, Chenopodiaceae, and Brassicaceae, allows for distinct recognition of anthropogenic activities throughout the whole transect. The diversity and distribution of diatoms also support the palynological data in response to climate-induced and anthropogenic ecological changes. Furthermore, grain size, geochemistry (TOC/TN ratio with stable carbon isotope), and magnetic susceptibility data offer crucial insights about the sediment's depositional settings and general mineralogical composition. Stable carbon isotope data shows C3 dominance in relatively humid areas and C4 dominance in semi-arid areas, suggesting climate-driven control over sediment organic matter composition. Canonical correspondence analysis (CCA) indicates that biotic variables (pollen, diatom, stable isotopic composition) are significantly controlled by modern precipitation and temperature. Redundancy analysis reveals a significant influence of current average temperature and precipitation on major element oxide variations in surface lake sediments. Therefore, we propose using palynological, stable carbon isotope, diatom data, along with grain size, environmental magnetism, and geochemistry, to establish a multiproxy modern analogue for quantitative palaeoclimatic reconstructions. As a result, this study provides the first modern analogues from a climate-sensitive region that separates the area under ISM influence from an area with meager precipitation in western India.

Determination of water quality and trophic level by using epilithic diatoms in Büyükçekmece Reservoir

In this study, the composition, distribution, and seasonal changes of epilithic diatoms were investigated to reveal the water quality and trophic level of Büyükçekmece Reservoir, which is one of the essential freshwater sources for İstanbul, Türkiye. Water and diatom samples were collected on the same day from all stations, and sampling was only on one day for a specific sampling season. Seventy-six taxa belonging to 30 genera were identified, two of which were centric and 74 were pennate diatoms; 12 of the epilithic species were newly-reported diatoms for the Büyükçekmece Reservoir. The highest number of epilithic diatom species was obtained in November, and the lowest was in February. According to relative abundance, Gomphonella olivacea was abundant in February, Cymbella lange-bertalotii in May, and Cocconeis placentula in August and November. According to the diatom-based water quality indices, the Büyükçekmece Reservoir belongs to I (very good, oligotrophic) and II (good, meso-oligotrophic) water quality classes. Redundancy analysis was used to reveal the association of epilithic diatom species with ecological variables, and it was determined that Silicate-Si, Ammonium-N, and temperature were the most effective variables in the distribution of epilithic diatoms.

Seasonal Distribution and Diversity of Epipelic Diatoms in the Lower Zab River

Seasonal Distribution and Diversity of Epipelic Diatoms in the Lower Zab River

Benthic Diatoms on Macrophytes of the Israeli Mediterranean Coast

Benthic diatoms have been studied in different areas of the Mediterranean Sea, but no data have been available for Israeli coastal waters until the present time. In this work, the composition, ecology, and phytogeography of diatoms of the macrophytes epiphyton are presented for the first time. Altogether, 85 diatom taxa were found among the epiphyton of 25 species of green, brown, and red macroalgae from the Israeli coast between March and May of 2021. These diatoms represent three classes, 17 orders, 26 families, and 41 genera. The taxonomic composition, ecology, and phytogeography of species are discussed. The distribution of diatoms are compared to that of other macrophytes and anthropogenic loads across the shoreline. The dominant species are given. Ecological characteristics and abundance in communities of revealed species are represented and statistically analyzed. The index of saprobity S varies between 1.69–2.71. Sites that stressed aquatic communities are indicated. The influence of the anthropogenic loads on the coastal territories is defined as a major factor that stimulated diatom species richness. Sites with anthropogenic stress for aquatic communities are indicated. Based on the composition of bioindicators, it is concluded that the section of the Israeli coast studied is oligo-mesotrophic compared to the eutrophic Gulf of Tartus.

Water mass influence on spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores in the western Barents Sea

Arctic phytoplankton are highly sensitive to seawater physical and chemical conditions, especially in the context of rapid climate change and sea ice loss. We studied the spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores, and clarified their associations with light, temperature and nutrients in the western Barents Sea in late summer 2017, and winter, spring and early summer 2018. Diatoms, composed mainly of Chaetoceros, Fragilariopsis and Thalassiosira, bloomed in spring at the southern border of the marginal ice zone with mean abundance of 1.1 × 106 cells L−1 and biomass of 119.5 µg C L−1, and were observed to follow the retreat of sea ice in the Arctic water to the north at the shelf break near Nansen Basin, contributing to the progression of the summer situation. Dinoflagellates flourished in surface waters south of Svalbard in summer, with maxima of 2.2 × 105 cells L−1 and 78.2 µg C L−1. High abundances and calcite mass of coccolithophores were detected in the southern Barents Sea and southwest of Svalbard in summer, with maxima of 3.3 × 105 cells L−1 and 4.7 µg C L−1. Two distinct phytoplankton assemblages, closely linked with Atlantic water and Arctic water, were geographically separated by the Polar Front in two summers, with a percent similarity below 11.9%, suggesting great influence of the two water masses on large-scale distributions of phytoplankton. Redundancy analysis revealed that temperature was one of the most important factors in shaping the seasonal distributions of diatoms, while irradiance showed positive correlation with dominant dinoflagellates of each season. From the perspectives of phytoplankton composition and carbon biomass, our findings highlight the governing effect of physical seawater conditions on driving seasonal patterns of phytoplankton biogeography, as well as the pivotal role of nutrients in supporting the phytoplankton growing seasons in the western Barents Sea.

Major Diatom Microfossils from the Arctic Region: A Review

Abstract Diatoms-the unicellular, eukaryotic, photosynthetic phytoplankton belonging to Class Bacillariophyceae are an excellent tool to understand past ocean surface conditions, especially in high latitude regions. Along with sea surface temperature and sea ice, which they are primarily sensitive to, diatom assemblages could potentially be used to record runoff from melting glaciers and atmospheric teleconnections such as North Atlantic Oscillations (NAO) in Arctic fjords. However, understanding the ecology and geographical distribution of diatoms is extremely important before they can be used for palaeoceanographic reconstructions. In this study, four significant Arctic diatoms namely Bacterosira bathyomphala, Fragilariopsis cylindrus, Fragilaripsis oceanica and Thalassiosira antarctica var. borealis resting spores (R.S.) have been reviewed to understand their current status in their use for palaeoceanographic reconstructions. These four diatoms have been selected as they represent a typical Arctic environment. Numerous studies in the past thirty years had classified these diatoms into different assemblage groups, indicating specific ocean surface conditions. Here, we review the previous studies and to present the up-to-date classification of these species. We also compared the change in abundance of these four species through mid to late Holocene and modern period to their respective sea surface temperature and sea ice reconstructions, to show the robustness of their usage in palaeoceanographic reconstructions. The findings of this study will help to understand the up-to-date ecological characteristics of Arctic diatoms used in palaeoceanographic as well as palaeoecological reconstructions and the gap areas in diatom research such as a requirement for pan Arctic Sea ice diatom dataset.

Epilithic Diatom Assemblages and Indicators for the Assessment of Water Quality of Munzur Stream, Turkey

The epilithic diatoms of Munzur Stream, together with the chemistry and physical variables of the water, were examined in the samples taken annually from 3 stations on the creek between October 2016 and September 2017. A total of 69 diatom taxa were identified benthic habitat. Cocconeis placentula, Cymbella affinis, Cymbella excisiformis , Didymosphenia geminata, Gomphonema olivaceum, and Hannaea arcus became diatoms at all that reached significant relative abundance. Shannon-diversity (H’), species evenness (J’), species richness (S) in each station varied between stations and months. Regarding diversity (H), values ranged from 1.54 (in December, at S3) to 2.99 (in October, at S3). Evenness ranged from 0.09 to 0.22 at station S3 in September (at S1, in September). Evenness ranged from 0.09 at site S3 in September, to 0.22 at S1, in September. All stations and species were close to 1 value. Canonical correspondence analysis indicated that three environmental variables (TN,TP, PO4-3) significantly affected the distribution of epilithic diatom. The studied part of stream was characterized by the species susceptible to nutrients such as Didymosphenia geminata, Cymbella excisiformis and Hannaea arcus which are found in the regions located in high lands having advanced ecological status. The results of the present study highlighted the importance of diatoms as a bio-indicator for health condition of a stream.

Ecological impacts of dam construction on epilithic diatom communities in estuaries: A case study of the Korean peninsula

This study, spanning 2016 to 2018, investigated diatom distribution in 324 Korean Peninsula estuaries, emphasizing the ecological impact of artificial dams. Examining environmental and biological variables, we focused on dam construction. OPEN estuaries exhibited higher urban/forest land cover and had more alkaline, saline, conductive, and oxygen-rich water. In CLOSE estuaries, agricultural farmland and nitrogen compound concentrations were higher. Dams in CLOSE estuaries correlated with lower pH, salinity, electrical conductivity, and dissolved oxygen. Regional variations were evident, with WEST OPEN estuaries showing higher salinity, turbidity, chemical oxygen demand, and total phosphorus. SOUTH estuaries displayed intermediate characteristics, while EAST OPEN estuaries had higher dissolved oxygen but lower temperature and turbidity.Diverse epilithic diatoms were identified, with OPEN estuaries displaying greater species richness, primarily dominated by Nitzschia inconspicua Grunow. CLOSE estuaries, conversely, exhibited higher richness with a different subdominant species. Indicator species analysis revealed taxa specific to estuaries and sea areas, with CLOSE ones exhibiting lower salinity and higher nitrogen/phosphorus concentrations. Nitzschia inconspicua dominated all estuaries, but subdominant species varied; N. fonticola (Grunow) Grunow in OPEN, N. paleaceae (Grunow) Grunow in CLOSE. CLOSE estuaries had higher species richness. In the West Sea, turbidity and TP levels affected diatom growth, with dams exacerbating turbidity and potentially disrupting the food chain.Results underscored intricate interactions between dams, land use, and diatom communities, offering foundational data for ecosystem management and biodiversity conservation in Korean Peninsula estuaries. Understanding the ecological consequences of artificial dams on diatom distribution is crucial for preserving estuarine health. Future research is recommended to explore additional factors influencing these ecosystems, particularly focusing on various organisms in West Sea estuaries for effective ecosystem management and conservation.

Net-phytoplankton communities and influencing factors in the Antarctic Peninsula region in the late austral summer 2019/2020

The waters near the Antarctic Peninsula are characterized with unique oceanographic conditions and rich krill resources. Based on samples collected around the South Shetland Islands (SSI) in austral summer of 2019/2020, the net- phytoplankton community structure and relevant major biotic and abiotic influencing factors were investigated. Eighty-one taxa were identified by light microscope, and diatoms were the most abundant group. The most abundant species were Chaetoceros atlanticus, C. criophilus, C. dichaeta, Fragilariopsis kerguelensis and Pseudo−nitzschia lineola. The abundance and Shannon-Weaver index of net-phytoplankton ranged from 100 to 2.64×107 cells/m3 and 0.0747 to 4.0176 respectively, with significantly low values detected in the Bransfield Strait (BS) and high values in the west of the SSI. The dissimilarity was mainly caused by the differences in abundance of diatoms (including Thalassiothrix antarctica and the species in genus Rhizosolenia, Chaetoceros, Fragilariophsis). These diatoms and Dictyocha speculum were found in higher abundance in the west of the SSI, while Corethron pennatum and cryptophytes were found in higher abundance in the BS. Combined with acoustic density of krill and environmental data (Sea Surface Temperature and Sea Ice Concentration). The multivariate analysis suggested that phytoplankton community was positively affected by the SST, and the acoustic- derived krill density would be associated with the spatial distribution of pennate diatoms. This study enhances the knowledge about the selective feeding for krill and provides ecological implications for the Antarctic marine ecosystem.

Influence of Some Abiotic Factors on the Diatom Densities in the Mezam River (Bamenda, North-West Cameroon)

Wetlands of the city of Bamenda are characterized by intense agricultural activities. The resulting consequences are aquatic pollution. The management of these wetlands requires the study of the animal and plant communities found there. Diatoms are known to be good markers of environmental change. The aim of the study was to determine the influence of some abiotic parameters on the diatom densities of the Mezam river. The study was conducted from January to December 2022. Some physicochemical parameters were measured in situ. Water samples were collected and transported to the laboratory for the measurement of nitrates, total phosphorus, carbon dioxide and biological oxygen demand. The diatoms were sampled and analyzed in the laboratory. Factorial axis 2 (0.47%) of correspondence factor analysis opposed the positive variables (conductivity, total dissolved solids and salinity) to the negative variables (water temperature, pH, nitrates, total phosphorus, oxidability, carbon dioxide and alkalinity). Study sites showed a mineralization gradient going from upstream (Site 1) to downstream (Site 3). Total species richness amounted to 4 classes divided in 18 families, 21 genera and 43 species. The most dominating family was Naviculaceae with 10 species. Multiple component analysis showed, in different study sites, the correlation between chemical parameters and density of different genera. The more the site was polluted, the more the density of Navicula, Tabellaria, Melosira and Coscinodiscus increased. On the contrary, the less the site was polluted, the more the density of Cyclotella, Gomphonema, Cocconeis, Gyrosigma, Synedra increased. These results showed that the distribution of diatoms in the different study sites was influenced by a set of conditions related to physicochemical parameters, but more on their densities.

Assessing diatom distribution in Cambay Basin, Western Arabian Sea: impacts of oil spillage and chemical variables.

Freshwater and marine diatoms produce the majority of the oxygen in aquatic systems. Estimates range from 12,000 to 30,000 species, and spatial distribution varies globally. There is significant variation in diatom diversity based on geographical and environmental conditions as well as the physicochemical characteristics of the habitat. Therefore, understanding the underlying factors that contribute to changes in diatom community structures requires a comprehensive understanding of taxons. A study of diatom assemblages from the Cambay Basin, Western Arabian Sea, was conducted, particularly on oil fields. A total of 37 samples were collected; nine were from oil fields. We evaluated micro-oil spills using Fourier transform infrared (FTIR) analysis and microscopic techniques. Correlations were established through the ordination analysis of pernicious physical and chemical water variables (BOD, COD, TDS, pH, temperature, and DO), including principal component analysis (PCA). The oil field sites showed more total dissolved solids (TDS) and chemical oxygen demand (COD) than the respective marine control sites. The study does not display a cause-and-effect relationship, but we observed a positive correlation between increasing silica concentrations and diatom growth in oil fields. In contrast, high aluminium concentrations in oil fields negatively impacted the growth of diatom assemblage and abundance. When surveyed in nine oil fields, we found that Gomphonella pseudosphaerophorum and Nitzschia palea are well adapted to oil concentrations up to 40 ppm.

무등산국립공원의 부착규조류 분포와 생물학적 수질평가

This survey was conducted to evaluate the distribution and biological water quality of epilithic diatoms from April to September 2022 by selecting a total of 17sites in Mudeungsan National Park, Korea. Environmental factors were analyzed such as water temperature, pH, electrical conductivity, BOD, TN and TP. A total of 111 species of epilithic diatoms appeared, and the dominant species were 13 species including Achnanthes convergens, Cocconeis placentula var. lineata, and Gomphonema clevei. Among dominant species, C. placentula var. lineata appeared as the dominant species 13times, showing the highest number of appearances. Among the ecological taxa, the relative frequencies of saproxenous group ranged from 20.63 to 99.57%, saprophilous group ranged from 0 to 50.08%. In evaluation of biological water quality, TDI was 12.5 ~ 99.7, water quality grade was E ~ A, DAIpo was 38.22 ~ 99.79, and water quality was D ~ A grade. In conclusion, the most representative epilithic diatom of Mudeungsan National Park was C. placentula var. lineata in terms of appearance number and dominance frequency. Biological water quality assessments are mostly in good condition, but some points appear to require continuous monitoring of the aquatic environment.

Diversity of Diatom Algae in the Lena Delta Nature Reserve and the Adjacent Territory in the Specific Ecological Factors of the Arctic

A total of 413 diatom taxa were known for aquatic habitats of the Lena Delta Nature Reserve. We identified 385 taxa in 14 small tundra lakes near the reserve that significantly enriched the diatom diversity of the region (666 taxa including definitions to the genus level). Thus, the species composition of diatoms in the reserve and adjacent territories was increased by 278 species. We showed that the species of the genera Pinnularia (57) and Eunotia (51) have predominance at the family and generic levels. The index of intraspecific variability Ssp./Sp. for the lakes of the reserve was 1.11, and that for the lakes of the Tiksi region 1.14, which is typical for high-latitude and high-mountain communities. The number of rare or endangered species varied in different lakes from 1 to 10, totaling 42 species for the entire study area. Bioindication has shown that potentially threatened species prefer moderate temperatures, and slightly acidic or neutral environments free from organic pollution. A comparative analysis of the species composition of diatoms in the vicinity of the Lena Delta and other northern water bodies of Yakutia and the Arctic Islands showed that the species composition of each lake in the Arctic has a discernably different species distribution. The indicator characteristics show a certain response of the species composition of diatoms to changes in salinity, pH, and organic pollution. Regularities in the spatial distribution of diatoms in the study area were revealed in connection with the environmental variables of their habitat. Statistical mapping of diatom diversity data and bioindicators revealed a pronounced response to point pollution, and also let us assume the influence of summer northeast winds on species composition of the studied lake communities. We suggest that the high diversity inherent in the diatom lakes of the Tiksi coastal zone, which can even be updated in further studies, can be considered as a property of coastal biota inherent in ecotones. Since it is in the coastal Tiksi region that a surge in the number of species is observed, this region can be considered not only an ecotone, but also a hotspot of diatom diversity. The results of the study are important for developing the basis for monitoring biodiversity under the conditions of anthropogenic and climatic changes in the Arctic.

Impacts of anthropogenic pressures on underwater light conditions and diatom functional group distributions in mountain lakes

Underwater light availability and exposure of ultraviolet radiation (UV) in mountain lakes is mainly controlled by dissolved organic matter and ice cover. However, both of these factors are affected by climate warming and other anthropogenic pressures. Still, little is known of the impacts of long-term fluctuations in underwater light conditions onto functional distribution of diatoms, species sensitive to changes in climate and UV penetration in mountain lakes. Two mountain lakes in the Italian Alps were analysed using paleolimnological approaches to investigate impacts of anthropogenic pressures (e.g., climate warming, acidification) on underwater light availability, exposure to UV and diatom functional group distributions, focusing on the post-industrial era. Contemporary diatom communities were collected from the main habitats in the shallow, high irradiance littoral zones of these lakes and geochemical proxies describing the development of lake-water transparency and carbon dynamics were analyzed from the sediment cores covering the time period from ca. 1400 CE to present. The geochemical data indicate that cultural acidification decreased lake-water organic carbon concentrations in both lakes, which suggests increased light availability and UV exposure during the past century. The responses of the studied lakes to anthropogenic pressures varied, as the lake situated at a lower altitude with a larger catchment showed only a few biotic changes indicating higher resilience, whereas the lake situated at higher altitude showed distinct changes in its ecological status. In this alpine lake, almost 30% of the diatom functional groups shifted from benthic to planktic during the post-industrial era. The role of increased light availability and UV exposure as a driver of diatom functional group distributions could not be unambiguously separated, and such diatom assemblage changes have been shown in many regions and most closely linked to a warming climate. However, low guild functional groups, prevalent also in the contemporary samples from the shallow littoral zone, dominated the diatom communities throughout the studied period, suggesting high tolerance to UV radiation.

The niche of a stress-tolerant specialist, Dinophysis acuminata, in a coastal upwelling system

Dinophysis acuminata, the main cause of shellfish harvesting bans in Europe, blooms in the Galician Rías (NW Spain) throughout the upwelling season (ca. March to September). Here we illustrate rapid changes in vertical and across ría-shelf distributions of diatoms and dinoflagellates (including D. acuminata vegetative and small cells) in Ría de Pontevedra (RP) and Ría de Vigo (RV) during transitions from spin-down to spin-up phases of upwelling cycles. A subniche approach based on a Within Outlying Mean Index (WitOMI) showed that under the transient environmental conditions met during the cruise, both vegetative and small cells of D. acuminata colonized the Ria and Mid-shelf subniches, exhibiting good tolerance and extremely high marginality, in particular the small cells. Bottom-up (abiotic) control overwhelmed biological constraints, and shelf waters became a more favourable environment than the Rías. Contrasting higher biotic constraints inside the Rías were found for the small cells, with a subniche possibly controlled by unsuitable physiological status (notwithstanding the higher density) of the vegetative cell population. Results here on behaviour (vertical positioning) and physiological traits (high tolerance but very specialized niche) of D. acuminata give new insights into the ability of this species to remain in the upwelling circulation system. Higher shelf-ría exchanges in the Ría (RP) with more dense and persistent D. acuminata blooms reveal the relevance of transient event-scales and species- and site-specific characteristics to the fate of these blooms. Earlier statements about simple linear relationships between average upwelling intensities and the recurrence of Harmful algae bloom (HAB) events in the Galician Rías Baixas are questioned.

The Relationship between Rainfall Pattern and Epilithic Diatoms in Four Streams of Central-Western Korea for Three Years (2013–2015)

To study the effect of rainfall patterns on diatom communities in four major central western streams on the Korean Peninsula during the monsoon seasons of 2013 through 2015, we measured precipitation, environmental factors, and epilithic diatoms at 42 sites before (May) and after (August and September) each monsoon. The Mangyeonggang river and Sapgyocheon stream (SS) had a high percentage of low-permeability soil, and the stream had the highest proportion (49.1%) of surrounding land in urban areas. Precipitation and precipitation frequency was closely correlated with electrical conductivity and nutrients, and this was particularly evident in SS. Epilithic diatom abundance for the most abundant species as, Navicula minima, decreased in the stream in 2013 and 2014 and increased in 2015 when precipitation and precipitation frequency were low. This was not clearly distinguishable in the ecological characteristics of each watercourse's indicator species, except in SS. The dynamic community index was highest in 2015 (ca. 5.50), and the annual changes in the index were clearly shown in SS. The precipitation pattern and the dynamic community index were negatively correlated (r = -0.026~-0.385), and the precipitation within 2 weeks (r = -0.480 for SS) before the second sampling and the frequency of 10 mm of precipitation were closely correlated in the stream (r = -0.450 for SS). The distribution of epilithic diatoms in the four watercourses is therefore affected by monsoon precipitation and precipitation frequency, and the dynamic community index is determined by soil characteristics and land use.

Quantitative relationship between surface sedimentary diatoms and water depth in North-Central Bohai Bay, China

To study the quantitative relationship between surface sedimentary diatoms and water depth, 67 surface samples were collected for diatom analysis on eight profiles with water depth variation from the muddy intertidal zone to the shallow sea area in North-Central Bohai Bay, China. The results showed that the distribution of diatoms changed significantly in response to the change in water depth. Furthermore, the quantitative relationship between the distribution of dominant diatom species, their assemblages, and the water depth was established. The water depth optima for seven dominant species such as Cyclotella striata/stylorum, Paralia sulcata, and Coscinodiscus perforatus and the water depth indication range of seven diatom assemblages were obtained in the study area above the water depth (elevation) of −10 m. The quantitative relationship between surface sedimentary diatoms and water depth provides a proxy index for diatom-paleo-water depth reconstruction in the strata in Bohai Bay, China.©2023 China Geology Editorial Office.

Identification of Diatoms in the Upstream, Middle, and Downstream Ciliwung River as a Diagnostic Tool for Drowning

Drowning is death caused by asphyxia due to the aspiration of fluids into the airways or lungs, resulting in airway obstruction within 24 hours. One of the examinations to establish the diagnosis of drowning victims is a laboratory examination of diatom identification. This research aims to know the morphological description and types of diatoms that live along the Upper, Middle, and Lower Ciliwung Watersheds, to facilitate the identification of drowning victims found in the Ciliwung River. The research design is qualitative descriptive. The data in this study were the results of observations and analysis of Ciliwung river water samples at the Research Laboratory of the Faculty of Medicine, Indonesian Christian University. The study's results found 17 different species at the Katulampa Dam, 19 at the Ciliwung Bridge, and 14 at the Manggarai Sluice Gate. From a total of 22 species of diatoms found, overall, the widest distribution was Nitzschia sp, Navicula sp, Fragilaria sp, and Cyclotella sp. The distribution and types of diatoms found are closely related to current velocity and water discharge, temperature, and river turbidity.

Diatom distribution in Holocene sediments from the northern West Caroline Basin (western equatorial Pacific) and their environmental significance

Diatoms are an important component of submarine biogenic sediments and often used for carrying out palaeoceanographical reconstructions. To understand the relationship between diatoms and environment in the western equatorial Pacific, diatoms from the Holocene sediments in the northern West Caroline Basin were selected for analysis. We made quantitative statistics on diatoms and divided diatom assemblages through cluster analysis. A total of 53 species or varieties of diatoms belonging to 22 genera were identified. The range of diatom abundance was 0-88,373 valves/g. The diatoms found were mainly oceanic warm-water species. Overall, Azpeitia nodulifera was the species with the highest contribution, followed by Hemidiscus cuneiformis and Thalassiosira pacifica with these three species together accounting for approximately 80% in this area. We identified four diatom groupings and divided the study area into three regions. Diatom assemblage I in the West Caroline Basin was mainly affected by the North Equatorial Counter Current (NECC), Antarctic Intermediate Water (AAIW) and upwelling, and the supply of nutrients was relatively high. Assemblage II in the West Caroline Ridge was less influenced by currents, and thus had lower abundance and species diversity than assemblage I. The complex diatom assemblages in the Yap Trench were probably controlled by Upper Circumpolar Deep Water (UCPW) and Lower Circumpolar Deep Water (LCPW).